X-rays have been used for imaging ever since they were discovered, more than a century ago. With their relatively weak interaction with matter and their short wavelength, X-rays are perfectly fit for high-resolution imaging in 2D, and especially 3D (tomography), of thick objects.
Modern synchrotron sources are able to produce X-rays that have good transverse and longitudinal coherence properties. The ability of confining the photons to the smallest possible phase space volume opens the possibility of modelizing accurately and unabiguously the interaction of the incoming wave with a sample. This opportunity has been seized in the last few years to create a different, lensless, mode of imaging. Such techniques, now most commonly described as "Coherent Diffractive Imaging" use "software lenses" to eliminate sources of image deteriorations brought about by X-ray lenses.
My research focuses on the application of some of these lensless techniques and on the data analysis techniques needed for image reconstruction. Currently of particular interest to me is the application of ptychography for high-resolution, and high-contrast 3D imaging.
Introduced in electron microscopy by Hegerl and Hoppe in the early 1970s, "ptychography" (pronounced "tychography") is an imaging method that combines diffraction data from multiple datasets obtained by scanning a finite illumination on an extended specimen. It was recognized early on that this approach provides sufficient overdetermination to solve the phase problem. Yet efficient algorithms to do so appeared only a few years ago. In the last few years, my colleagues and I have developed the method further, and devised an improved reconstruction method that extracts from the data both the image of the specimen and the illumination function.
The main hurdles for application of ptychography have now been cleared, and it is routinely applied at the cSAXS beamline at the Swiss Light Source, where I did my first post-doc. Ptychography setups are now planned or under construction in most major synchrotron facilities, often in combination with other scanning methods, such as fluorescence mapping or scanning transmission X-ray microscopy (STXM).